Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

712
FXUS63 KLOT 040915
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
315 AM CST Sun Jan 4 2026

.KEY MESSAGES...

- There is a low chance (20%) for a brief period of freezing
  rain and sleet this evening north of the I-90 corridor. Any
  wintry precipitation that develops may lead to localized slick
  spots.

- Above average temperatures return Monday through the end of
  the upcoming workweek.

&&

.DISCUSSION...
Issued at 315 AM CST Sun Jan 4 2026

Through Tonight:

Early this morning, a disturbance is evident over the High
Plains on water vapor imagery as an upper shortwave is just now
getting spun up. This clipper system will mature across the
northern Plains today and move into the upper Midwest this
evening. A plume of wintry precipitation will blossom out ahead
of the system over Minnesota this afternoon and primarily target
Wisconsin and the UP of Michigan this evening, but could clip
far northern portions of our CWA. The bulk of the synoptic
forcing will focus into Wisconsin being on the nose of a 50-55
kt low level jet and within the left exit region of a
cyclonically-curved upper jet max. But the low precip chances
locally moreso boil down to a lack of low level moisture south
of the state line that may not be ample to support precip.
Forecast soundings for this evening depict a stout low level
warm nose with a sub-freezing boundary layer. This means that if
precip does fall on the CWA this evening, freezing rain and
freezing drizzle will be the most likely P-types, but some sleet
will also be possible. Probs for even a trace of precip from
the HREF max out at only 10% in our CWA and extend roughly along
a Rockton to Evanston line, highest up along the WI state line.
The global camps and ensemble systems are a bit more excited,
most notably the EPS. But it`s also worth mentioning that
ensemble precip probs within our CWA have been on a steady
downward trend, especially noted with the most recent EPS run
from last evening. At worst, a glaze of ice will accumulate here
and there and lead to localized slick spots across our far
north. More likely scenario though is that the area remains dry
and we see no impacts out of this. Favorable time window is end
of the afternoon into the latter part of this evening. In the
forecast, maintained slight chance PoPs just north of the I-90
corridor.

In other news, we`re starting the day beneath a 2 to 4 kft
stratus deck that guidance is really struggling with. Forecast
soundings would suggest that the deck should start to scatter
later this morning but skies are likely to remain mostly cloudy
throughout the day, especially with mid-high coverage moving in
during the afternoon ahead of the clipper. Highs this afternoon
are forecast in the lower to middle 30s, give or take a degree
or two depending on sky conditions throughout the day. The
aforementioned low level jet building into the region will
provide marginally gusty southerly winds this evening into
tonight and gusts as high as 20 to 25 mph are expected. Low
level warm advection with more low stratus anticipated late
tonight will keep temperatures near-steady through the night. By
Monday morning, most sites may only be a degree or two cooler
than this afternoon with lows forecast in the upper 20s to
around 30 degrees.

Doom


Monday through Saturday:

A quasi-zonal (west-to-east oriented) mid and upper level flow
pattern will persist across the mid section of the country
through midweek. This will generally result in a milder (above
average temperatures) weather pattern for our area for much of
the first full work week of 2026. However, it will not
necessarily be a sunny period of fair weather through the week.
Instead, it is likely we will experience a period of gloomy
weather, particularly on Tuesday. On Tuesday, model and ensemble
guidance remain in good agreement in tracking a quick moving
impulse and an associated surface low eastward right across far
northern IL. While we won`t necessarily experience a lot of
precipitation with this system, low clouds, drizzle and a
possible period of foggy weather appears to be a good bet across
a good chunk of northern IL. Temperatures both Monday and
Tuesday will remain above freezing, so there is no threat of
freezing precipitation on Tuesday.

Primarily dry and mild weather is expected for Wednesday, and
much of the daylight hours Thursday, and we could see more sun
shine for Wednesday. Temperatures both days are thus forecast
to be solidly in the mid to upper 40s. Some 50+ degree readings
are also possible, particularly south of I-80. Rain chances then
look to increase (50%+) Thursday evening and night in response
to the next upper trough ejecting out of the Desert Southwest.
Unfortunately, forecast uncertainty begins to increase
substantially Thursday night through Friday, owing to increasing
ensemble spread with the evolution of the trough ejecting out
of the Desert Southwest and how it may, or may not, interact
with a second northern stream trough likely to quickly dig in
across the Upper Midwest late in the week. For this reason, I
made no chances to the NBM forecast, which continues to
advertise chance POPs areawide on Friday. Temperatures (and
P-Types) on Friday will largely be driven by the track of the
area surface low pressure expected to accompany the parent upper
level trough. At this time, there remains multiple camps, with
some tracking the low to our south with cooler conditions, while
others track the low to our northwest with much milder weather.

While forecast confidence in the Thursday night through Friday
timeframe is low at this time, there is a strong signal that we
will trend back to a period of colder (more typical) weather
next weekend.

KJB

&&

.AVIATION /06Z TAFS THROUGH 12Z MONDAY/...
Issued at 1057 PM CST Sat Jan 3 2026

Aviation forecast concerns for the 06 TAFs:

- Period of MVFR ceilings possible late tonight and potentially
  for a portion of the day Sunday. (40-50% chance).

- Low-end chance (~15%) for patchy light freezing drizzle late
  Sunday/Sunday evening mainly north of terminals near the
  IL/WI border.

- Chance (30%) for marginal LLWS conditions Sunday evening in
  association with a 45 kt low level jet.

Extensive stratus deck persists across the region late this
evening. Ceilings have been gradually lowering through VFR range
across the terminals, and may dip to high-MVFR before scattering
toward daybreak, especially at KRFD. AS mentioned previously,
model guidance has not been handling the stratus well, so
timing/occurrence of scattering low clouds remains of somewhat
low confidence, though some breaks have developed upstream
across parts of central/western WI per satellite imagery.
If it does occur, scattering of low clouds may not last too
long Sunday morning, as low-level flow turns southerly and
guidance suggests some potential for some redevelopment of MVFR
CIGs for a time Sunday. Forecast soundings indicate scattering
again by evening, though confidence remains low in these trends
and can`t rule out additional MVFR development later Sunday
night. Models have consistently been indicating a period of
mixed wintry precip across WI and near the IL/WI border late
Sunday into Sunday night. Current indications are this is likely
to remain north of the terminals, though there is a low (~15%)
chance that some of this could briefly affect especially KRFD.
If so, it would likely be brief, light and of little impact.

Wind-wise, light northwest winds will turn southerly mid-late
Sunday morning and increase in speed during the afternoon and
evening as an area of low pressure develops into the upper
Mississippi Valley. Guidance continues to indicate winds may be
south-southeast during the afternoon/early evening. A west-
southwest low level jet is forecast to develop Sunday evening,
roughly 45 kts at ~2000 feet. It`s possible that surface winds
could be a little gusty during that time if surface mixing is
more pronounced, which would lessen the LLWS magnitude. For now
have not indicated LLWS in forecast but will monitor trends
with later issuances.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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